# SPDX-License-Identifier: GPL-2.0-only
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menu "Memory Management options"
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config SELECT_MEMORY_MODEL
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def_bool y
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depends on ARCH_SELECT_MEMORY_MODEL
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choice
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prompt "Memory model"
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depends on SELECT_MEMORY_MODEL
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default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
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default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
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default FLATMEM_MANUAL
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help
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This option allows you to change some of the ways that
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Linux manages its memory internally. Most users will
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only have one option here selected by the architecture
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configuration. This is normal.
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config FLATMEM_MANUAL
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bool "Flat Memory"
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depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
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help
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This option is best suited for non-NUMA systems with
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flat address space. The FLATMEM is the most efficient
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system in terms of performance and resource consumption
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and it is the best option for smaller systems.
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For systems that have holes in their physical address
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spaces and for features like NUMA and memory hotplug,
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choose "Sparse Memory".
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If unsure, choose this option (Flat Memory) over any other.
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config DISCONTIGMEM_MANUAL
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bool "Discontiguous Memory"
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depends on ARCH_DISCONTIGMEM_ENABLE
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help
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This option provides enhanced support for discontiguous
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memory systems, over FLATMEM. These systems have holes
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in their physical address spaces, and this option provides
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more efficient handling of these holes.
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Although "Discontiguous Memory" is still used by several
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architectures, it is considered deprecated in favor of
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"Sparse Memory".
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If unsure, choose "Sparse Memory" over this option.
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config SPARSEMEM_MANUAL
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bool "Sparse Memory"
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depends on ARCH_SPARSEMEM_ENABLE
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help
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This will be the only option for some systems, including
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memory hot-plug systems. This is normal.
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This option provides efficient support for systems with
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holes is their physical address space and allows memory
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hot-plug and hot-remove.
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If unsure, choose "Flat Memory" over this option.
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endchoice
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config DISCONTIGMEM
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def_bool y
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depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
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config SPARSEMEM
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def_bool y
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depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
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config FLATMEM
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def_bool y
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depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
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config FLAT_NODE_MEM_MAP
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def_bool y
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depends on !SPARSEMEM
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#
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# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
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# to represent different areas of memory. This variable allows
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# those dependencies to exist individually.
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#
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config NEED_MULTIPLE_NODES
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def_bool y
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depends on DISCONTIGMEM || NUMA
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#
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# SPARSEMEM_EXTREME (which is the default) does some bootmem
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# allocations when sparse_init() is called. If this cannot
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# be done on your architecture, select this option. However,
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# statically allocating the mem_section[] array can potentially
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# consume vast quantities of .bss, so be careful.
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#
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# This option will also potentially produce smaller runtime code
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# with gcc 3.4 and later.
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#
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config SPARSEMEM_STATIC
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bool
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#
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# Architecture platforms which require a two level mem_section in SPARSEMEM
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# must select this option. This is usually for architecture platforms with
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# an extremely sparse physical address space.
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#
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config SPARSEMEM_EXTREME
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def_bool y
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depends on SPARSEMEM && !SPARSEMEM_STATIC
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config SPARSEMEM_VMEMMAP_ENABLE
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bool
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config SPARSEMEM_VMEMMAP
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bool "Sparse Memory virtual memmap"
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depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
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default y
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help
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SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
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pfn_to_page and page_to_pfn operations. This is the most
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efficient option when sufficient kernel resources are available.
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config HAVE_MEMBLOCK_PHYS_MAP
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bool
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config HAVE_FAST_GUP
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depends on MMU
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bool
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# Don't discard allocated memory used to track "memory" and "reserved" memblocks
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# after early boot, so it can still be used to test for validity of memory.
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# Also, memblocks are updated with memory hot(un)plug.
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config ARCH_KEEP_MEMBLOCK
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bool
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# Keep arch NUMA mapping infrastructure post-init.
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config NUMA_KEEP_MEMINFO
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bool
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config MEMORY_ISOLATION
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bool
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#
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# Only be set on architectures that have completely implemented memory hotplug
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# feature. If you are not sure, don't touch it.
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#
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config HAVE_BOOTMEM_INFO_NODE
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def_bool n
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# eventually, we can have this option just 'select SPARSEMEM'
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config MEMORY_HOTPLUG
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bool "Allow for memory hot-add"
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select MEMORY_ISOLATION
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depends on SPARSEMEM || X86_64_ACPI_NUMA
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depends on ARCH_ENABLE_MEMORY_HOTPLUG
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depends on 64BIT || BROKEN
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select NUMA_KEEP_MEMINFO if NUMA
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config MEMORY_HOTPLUG_SPARSE
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def_bool y
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depends on SPARSEMEM && MEMORY_HOTPLUG
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config MEMORY_HOTPLUG_DEFAULT_ONLINE
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bool "Online the newly added memory blocks by default"
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depends on MEMORY_HOTPLUG
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help
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This option sets the default policy setting for memory hotplug
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onlining policy (/sys/devices/system/memory/auto_online_blocks) which
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determines what happens to newly added memory regions. Policy setting
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can always be changed at runtime.
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See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
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Say Y here if you want all hot-plugged memory blocks to appear in
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'online' state by default.
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Say N here if you want the default policy to keep all hot-plugged
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memory blocks in 'offline' state.
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config MEMORY_HOTREMOVE
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bool "Allow for memory hot remove"
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select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
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depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
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depends on MIGRATION
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# Heavily threaded applications may benefit from splitting the mm-wide
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# page_table_lock, so that faults on different parts of the user address
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# space can be handled with less contention: split it at this NR_CPUS.
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# Default to 4 for wider testing, though 8 might be more appropriate.
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# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
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# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
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# SPARC32 allocates multiple pte tables within a single page, and therefore
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# a per-page lock leads to problems when multiple tables need to be locked
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# at the same time (e.g. copy_page_range()).
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# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
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#
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config SPLIT_PTLOCK_CPUS
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int
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default "999999" if !MMU
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default "999999" if ARM && !CPU_CACHE_VIPT
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default "999999" if PARISC && !PA20
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default "999999" if SPARC32
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default "4"
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config ARCH_ENABLE_SPLIT_PMD_PTLOCK
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bool
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#
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# support for memory balloon
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config MEMORY_BALLOON
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bool
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#
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# support for memory balloon compaction
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config BALLOON_COMPACTION
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bool "Allow for balloon memory compaction/migration"
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def_bool y
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depends on COMPACTION && MEMORY_BALLOON
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help
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Memory fragmentation introduced by ballooning might reduce
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significantly the number of 2MB contiguous memory blocks that can be
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used within a guest, thus imposing performance penalties associated
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with the reduced number of transparent huge pages that could be used
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by the guest workload. Allowing the compaction & migration for memory
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pages enlisted as being part of memory balloon devices avoids the
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scenario aforementioned and helps improving memory defragmentation.
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#
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# support for memory compaction
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config COMPACTION
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bool "Allow for memory compaction"
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def_bool y
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select MIGRATION
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depends on MMU
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help
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Compaction is the only memory management component to form
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high order (larger physically contiguous) memory blocks
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reliably. The page allocator relies on compaction heavily and
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the lack of the feature can lead to unexpected OOM killer
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invocations for high order memory requests. You shouldn't
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disable this option unless there really is a strong reason for
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it and then we would be really interested to hear about that at
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linux-mm@kvack.org.
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#
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# support for free page reporting
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config PAGE_REPORTING
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bool "Free page reporting"
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def_bool n
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help
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Free page reporting allows for the incremental acquisition of
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free pages from the buddy allocator for the purpose of reporting
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those pages to another entity, such as a hypervisor, so that the
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memory can be freed within the host for other uses.
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#
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# support for page migration
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#
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config MIGRATION
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bool "Page migration"
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def_bool y
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depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
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help
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Allows the migration of the physical location of pages of processes
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while the virtual addresses are not changed. This is useful in
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two situations. The first is on NUMA systems to put pages nearer
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to the processors accessing. The second is when allocating huge
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pages as migration can relocate pages to satisfy a huge page
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allocation instead of reclaiming.
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config ARCH_ENABLE_HUGEPAGE_MIGRATION
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bool
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config ARCH_ENABLE_THP_MIGRATION
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bool
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config CONTIG_ALLOC
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def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
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config PHYS_ADDR_T_64BIT
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def_bool 64BIT
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config BOUNCE
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bool "Enable bounce buffers"
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default y
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depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
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help
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Enable bounce buffers for devices that cannot access
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the full range of memory available to the CPU. Enabled
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by default when ZONE_DMA or HIGHMEM is selected, but you
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may say n to override this.
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config VIRT_TO_BUS
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bool
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help
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An architecture should select this if it implements the
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deprecated interface virt_to_bus(). All new architectures
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should probably not select this.
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config MMU_NOTIFIER
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bool
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select SRCU
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select INTERVAL_TREE
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config KSM
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bool "Enable KSM for page merging"
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depends on MMU
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select XXHASH
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help
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Enable Kernel Samepage Merging: KSM periodically scans those areas
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of an application's address space that an app has advised may be
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mergeable. When it finds pages of identical content, it replaces
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the many instances by a single page with that content, so
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saving memory until one or another app needs to modify the content.
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Recommended for use with KVM, or with other duplicative applications.
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See Documentation/vm/ksm.rst for more information: KSM is inactive
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until a program has madvised that an area is MADV_MERGEABLE, and
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root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
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config DEFAULT_MMAP_MIN_ADDR
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int "Low address space to protect from user allocation"
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depends on MMU
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default 4096
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help
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This is the portion of low virtual memory which should be protected
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from userspace allocation. Keeping a user from writing to low pages
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can help reduce the impact of kernel NULL pointer bugs.
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For most ia64, ppc64 and x86 users with lots of address space
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a value of 65536 is reasonable and should cause no problems.
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On arm and other archs it should not be higher than 32768.
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Programs which use vm86 functionality or have some need to map
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this low address space will need CAP_SYS_RAWIO or disable this
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protection by setting the value to 0.
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This value can be changed after boot using the
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/proc/sys/vm/mmap_min_addr tunable.
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config ARCH_SUPPORTS_MEMORY_FAILURE
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bool
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config MEMORY_FAILURE
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depends on MMU
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depends on ARCH_SUPPORTS_MEMORY_FAILURE
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bool "Enable recovery from hardware memory errors"
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select MEMORY_ISOLATION
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select RAS
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help
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Enables code to recover from some memory failures on systems
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with MCA recovery. This allows a system to continue running
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even when some of its memory has uncorrected errors. This requires
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special hardware support and typically ECC memory.
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config HWPOISON_INJECT
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tristate "HWPoison pages injector"
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depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
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select PROC_PAGE_MONITOR
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config NOMMU_INITIAL_TRIM_EXCESS
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int "Turn on mmap() excess space trimming before booting"
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depends on !MMU
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default 1
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help
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The NOMMU mmap() frequently needs to allocate large contiguous chunks
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of memory on which to store mappings, but it can only ask the system
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allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
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more than it requires. To deal with this, mmap() is able to trim off
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the excess and return it to the allocator.
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If trimming is enabled, the excess is trimmed off and returned to the
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system allocator, which can cause extra fragmentation, particularly
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if there are a lot of transient processes.
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If trimming is disabled, the excess is kept, but not used, which for
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long-term mappings means that the space is wasted.
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Trimming can be dynamically controlled through a sysctl option
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(/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
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excess pages there must be before trimming should occur, or zero if
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no trimming is to occur.
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This option specifies the initial value of this option. The default
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of 1 says that all excess pages should be trimmed.
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See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
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config TRANSPARENT_HUGEPAGE
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bool "Transparent Hugepage Support"
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depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
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select COMPACTION
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select XARRAY_MULTI
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help
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Transparent Hugepages allows the kernel to use huge pages and
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huge tlb transparently to the applications whenever possible.
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This feature can improve computing performance to certain
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applications by speeding up page faults during memory
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allocation, by reducing the number of tlb misses and by speeding
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up the pagetable walking.
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If memory constrained on embedded, you may want to say N.
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choice
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prompt "Transparent Hugepage Support sysfs defaults"
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depends on TRANSPARENT_HUGEPAGE
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default TRANSPARENT_HUGEPAGE_ALWAYS
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help
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Selects the sysfs defaults for Transparent Hugepage Support.
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config TRANSPARENT_HUGEPAGE_ALWAYS
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bool "always"
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help
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Enabling Transparent Hugepage always, can increase the
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memory footprint of applications without a guaranteed
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benefit but it will work automatically for all applications.
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config TRANSPARENT_HUGEPAGE_MADVISE
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bool "madvise"
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help
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Enabling Transparent Hugepage madvise, will only provide a
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performance improvement benefit to the applications using
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madvise(MADV_HUGEPAGE) but it won't risk to increase the
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memory footprint of applications without a guaranteed
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benefit.
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endchoice
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config ARCH_WANTS_THP_SWAP
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def_bool n
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config THP_SWAP
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def_bool y
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depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP
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help
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Swap transparent huge pages in one piece, without splitting.
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XXX: For now, swap cluster backing transparent huge page
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will be split after swapout.
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For selection by architectures with reasonable THP sizes.
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#
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# UP and nommu archs use km based percpu allocator
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#
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config NEED_PER_CPU_KM
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depends on !SMP
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bool
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default y
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config CLEANCACHE
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bool "Enable cleancache driver to cache clean pages if tmem is present"
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help
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Cleancache can be thought of as a page-granularity victim cache
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for clean pages that the kernel's pageframe replacement algorithm
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(PFRA) would like to keep around, but can't since there isn't enough
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memory. So when the PFRA "evicts" a page, it first attempts to use
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cleancache code to put the data contained in that page into
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"transcendent memory", memory that is not directly accessible or
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addressable by the kernel and is of unknown and possibly
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time-varying size. And when a cleancache-enabled
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filesystem wishes to access a page in a file on disk, it first
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checks cleancache to see if it already contains it; if it does,
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the page is copied into the kernel and a disk access is avoided.
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When a transcendent memory driver is available (such as zcache or
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Xen transcendent memory), a significant I/O reduction
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may be achieved. When none is available, all cleancache calls
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are reduced to a single pointer-compare-against-NULL resulting
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in a negligible performance hit.
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If unsure, say Y to enable cleancache
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config FRONTSWAP
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bool "Enable frontswap to cache swap pages if tmem is present"
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depends on SWAP
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help
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Frontswap is so named because it can be thought of as the opposite
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of a "backing" store for a swap device. The data is stored into
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"transcendent memory", memory that is not directly accessible or
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addressable by the kernel and is of unknown and possibly
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time-varying size. When space in transcendent memory is available,
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a significant swap I/O reduction may be achieved. When none is
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available, all frontswap calls are reduced to a single pointer-
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compare-against-NULL resulting in a negligible performance hit
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and swap data is stored as normal on the matching swap device.
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If unsure, say Y to enable frontswap.
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config CMA
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bool "Contiguous Memory Allocator"
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depends on MMU
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select MIGRATION
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select MEMORY_ISOLATION
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help
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This enables the Contiguous Memory Allocator which allows other
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subsystems to allocate big physically-contiguous blocks of memory.
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CMA reserves a region of memory and allows only movable pages to
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be allocated from it. This way, the kernel can use the memory for
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pagecache and when a subsystem requests for contiguous area, the
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allocated pages are migrated away to serve the contiguous request.
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If unsure, say "n".
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config CMA_INACTIVE
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bool "CMA not active to system"
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depends on CMA
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help
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This forbids the CMA to active its pages to system memory, to keep
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page from CMA never be borrowed by system.
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If unsure, say "n".
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config CMA_DEBUG
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bool "CMA debug messages (DEVELOPMENT)"
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depends on DEBUG_KERNEL && CMA
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help
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Turns on debug messages in CMA. This produces KERN_DEBUG
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messages for every CMA call as well as various messages while
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processing calls such as dma_alloc_from_contiguous().
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This option does not affect warning and error messages.
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config CMA_DEBUGFS
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bool "CMA debugfs interface"
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depends on CMA && DEBUG_FS
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help
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Turns on the DebugFS interface for CMA.
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config CMA_DEBUGFS_BITMAP_HEX
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bool "CMA debugfs add bitmap_hex node"
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depends on CMA_DEBUGFS
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help
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Turns on the bitmap_hex node under DEBUGFS, shows the bitmap in hex
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format.
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config CMA_SYSFS
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bool "CMA information through sysfs interface"
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depends on CMA && SYSFS
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help
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This option exposes some sysfs attributes to get information
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from CMA.
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config CMA_AREAS
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int "Maximum count of the CMA areas"
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depends on CMA
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default 19 if NUMA
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default 7
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help
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CMA allows to create CMA areas for particular purpose, mainly,
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used as device private area. This parameter sets the maximum
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number of CMA area in the system.
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If unsure, leave the default value "7" in UMA and "19" in NUMA.
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config MEM_SOFT_DIRTY
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bool "Track memory changes"
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depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
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select PROC_PAGE_MONITOR
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help
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This option enables memory changes tracking by introducing a
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soft-dirty bit on pte-s. This bit it set when someone writes
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into a page just as regular dirty bit, but unlike the latter
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it can be cleared by hands.
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See Documentation/admin-guide/mm/soft-dirty.rst for more details.
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config ZSWAP
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bool "Compressed cache for swap pages (EXPERIMENTAL)"
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depends on FRONTSWAP && CRYPTO=y
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select ZPOOL
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help
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A lightweight compressed cache for swap pages. It takes
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pages that are in the process of being swapped out and attempts to
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compress them into a dynamically allocated RAM-based memory pool.
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This can result in a significant I/O reduction on swap device and,
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in the case where decompressing from RAM is faster that swap device
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reads, can also improve workload performance.
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This is marked experimental because it is a new feature (as of
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v3.11) that interacts heavily with memory reclaim. While these
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interactions don't cause any known issues on simple memory setups,
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they have not be fully explored on the large set of potential
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configurations and workloads that exist.
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choice
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prompt "Compressed cache for swap pages default compressor"
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depends on ZSWAP
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default ZSWAP_COMPRESSOR_DEFAULT_LZO
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help
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Selects the default compression algorithm for the compressed cache
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for swap pages.
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For an overview what kind of performance can be expected from
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a particular compression algorithm please refer to the benchmarks
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available at the following LWN page:
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https://lwn.net/Articles/751795/
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If in doubt, select 'LZO'.
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The selection made here can be overridden by using the kernel
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command line 'zswap.compressor=' option.
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config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
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bool "Deflate"
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select CRYPTO_DEFLATE
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help
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Use the Deflate algorithm as the default compression algorithm.
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config ZSWAP_COMPRESSOR_DEFAULT_LZO
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bool "LZO"
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select CRYPTO_LZO
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help
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Use the LZO algorithm as the default compression algorithm.
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config ZSWAP_COMPRESSOR_DEFAULT_842
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bool "842"
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select CRYPTO_842
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help
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Use the 842 algorithm as the default compression algorithm.
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config ZSWAP_COMPRESSOR_DEFAULT_LZ4
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bool "LZ4"
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select CRYPTO_LZ4
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help
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Use the LZ4 algorithm as the default compression algorithm.
|
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config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
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bool "LZ4HC"
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select CRYPTO_LZ4HC
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help
|
Use the LZ4HC algorithm as the default compression algorithm.
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config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
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bool "zstd"
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select CRYPTO_ZSTD
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help
|
Use the zstd algorithm as the default compression algorithm.
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endchoice
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config ZSWAP_COMPRESSOR_DEFAULT
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string
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depends on ZSWAP
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default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
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default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
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default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
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default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
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default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
|
default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
|
default ""
|
|
choice
|
prompt "Compressed cache for swap pages default allocator"
|
depends on ZSWAP
|
default ZSWAP_ZPOOL_DEFAULT_ZBUD
|
help
|
Selects the default allocator for the compressed cache for
|
swap pages.
|
The default is 'zbud' for compatibility, however please do
|
read the description of each of the allocators below before
|
making a right choice.
|
|
The selection made here can be overridden by using the kernel
|
command line 'zswap.zpool=' option.
|
|
config ZSWAP_ZPOOL_DEFAULT_ZBUD
|
bool "zbud"
|
select ZBUD
|
help
|
Use the zbud allocator as the default allocator.
|
|
config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
|
bool "z3fold"
|
select Z3FOLD
|
help
|
Use the z3fold allocator as the default allocator.
|
|
config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
|
bool "zsmalloc"
|
select ZSMALLOC
|
help
|
Use the zsmalloc allocator as the default allocator.
|
endchoice
|
|
config ZSWAP_ZPOOL_DEFAULT
|
string
|
depends on ZSWAP
|
default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
|
default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
|
default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
|
default ""
|
|
config ZSWAP_DEFAULT_ON
|
bool "Enable the compressed cache for swap pages by default"
|
depends on ZSWAP
|
help
|
If selected, the compressed cache for swap pages will be enabled
|
at boot, otherwise it will be disabled.
|
|
The selection made here can be overridden by using the kernel
|
command line 'zswap.enabled=' option.
|
|
config ZPOOL
|
tristate "Common API for compressed memory storage"
|
help
|
Compressed memory storage API. This allows using either zbud or
|
zsmalloc.
|
|
config ZBUD
|
tristate "Low (Up to 2x) density storage for compressed pages"
|
help
|
A special purpose allocator for storing compressed pages.
|
It is designed to store up to two compressed pages per physical
|
page. While this design limits storage density, it has simple and
|
deterministic reclaim properties that make it preferable to a higher
|
density approach when reclaim will be used.
|
|
config Z3FOLD
|
tristate "Up to 3x density storage for compressed pages"
|
depends on ZPOOL
|
help
|
A special purpose allocator for storing compressed pages.
|
It is designed to store up to three compressed pages per physical
|
page. It is a ZBUD derivative so the simplicity and determinism are
|
still there.
|
|
config ZSMALLOC
|
tristate "Memory allocator for compressed pages"
|
depends on MMU
|
help
|
zsmalloc is a slab-based memory allocator designed to store
|
compressed RAM pages. zsmalloc uses virtual memory mapping
|
in order to reduce fragmentation. However, this results in a
|
non-standard allocator interface where a handle, not a pointer, is
|
returned by an alloc(). This handle must be mapped in order to
|
access the allocated space.
|
|
config ZSMALLOC_STAT
|
bool "Export zsmalloc statistics"
|
depends on ZSMALLOC
|
select DEBUG_FS
|
help
|
This option enables code in the zsmalloc to collect various
|
statistics about whats happening in zsmalloc and exports that
|
information to userspace via debugfs.
|
If unsure, say N.
|
|
config GENERIC_EARLY_IOREMAP
|
bool
|
|
config MAX_STACK_SIZE_MB
|
int "Maximum user stack size for 32-bit processes (MB)"
|
default 80
|
range 8 2048
|
depends on STACK_GROWSUP && (!64BIT || COMPAT)
|
help
|
This is the maximum stack size in Megabytes in the VM layout of 32-bit
|
user processes when the stack grows upwards (currently only on parisc
|
arch). The stack will be located at the highest memory address minus
|
the given value, unless the RLIMIT_STACK hard limit is changed to a
|
smaller value in which case that is used.
|
|
A sane initial value is 80 MB.
|
|
config DEFERRED_STRUCT_PAGE_INIT
|
bool "Defer initialisation of struct pages to kthreads"
|
depends on SPARSEMEM
|
depends on !NEED_PER_CPU_KM
|
depends on 64BIT
|
select PADATA
|
help
|
Ordinarily all struct pages are initialised during early boot in a
|
single thread. On very large machines this can take a considerable
|
amount of time. If this option is set, large machines will bring up
|
a subset of memmap at boot and then initialise the rest in parallel.
|
This has a potential performance impact on tasks running early in the
|
lifetime of the system until these kthreads finish the
|
initialisation.
|
|
config PAGE_IDLE_FLAG
|
bool
|
select PAGE_EXTENSION if !64BIT
|
help
|
This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed
|
bit writers can set the state of the bit in the flags so that PTE
|
Accessed bit readers may avoid disturbance.
|
|
config IDLE_PAGE_TRACKING
|
bool "Enable idle page tracking"
|
depends on SYSFS && MMU
|
select PAGE_IDLE_FLAG
|
help
|
This feature allows to estimate the amount of user pages that have
|
not been touched during a given period of time. This information can
|
be useful to tune memory cgroup limits and/or for job placement
|
within a compute cluster.
|
|
See Documentation/admin-guide/mm/idle_page_tracking.rst for
|
more details.
|
|
config ARCH_HAS_PTE_DEVMAP
|
bool
|
|
config ZONE_DEVICE
|
bool "Device memory (pmem, HMM, etc...) hotplug support"
|
depends on MEMORY_HOTPLUG
|
depends on MEMORY_HOTREMOVE
|
depends on SPARSEMEM_VMEMMAP
|
depends on ARCH_HAS_PTE_DEVMAP
|
select XARRAY_MULTI
|
|
help
|
Device memory hotplug support allows for establishing pmem,
|
or other device driver discovered memory regions, in the
|
memmap. This allows pfn_to_page() lookups of otherwise
|
"device-physical" addresses which is needed for using a DAX
|
mapping in an O_DIRECT operation, among other things.
|
|
If FS_DAX is enabled, then say Y.
|
|
config DEV_PAGEMAP_OPS
|
bool
|
|
#
|
# Helpers to mirror range of the CPU page tables of a process into device page
|
# tables.
|
#
|
config HMM_MIRROR
|
bool
|
depends on MMU
|
|
config DEVICE_PRIVATE
|
bool "Unaddressable device memory (GPU memory, ...)"
|
depends on ZONE_DEVICE
|
select DEV_PAGEMAP_OPS
|
|
help
|
Allows creation of struct pages to represent unaddressable device
|
memory; i.e., memory that is only accessible from the device (or
|
group of devices). You likely also want to select HMM_MIRROR.
|
|
config VMAP_PFN
|
bool
|
|
config FRAME_VECTOR
|
bool
|
|
config ARCH_USES_HIGH_VMA_FLAGS
|
bool
|
config ARCH_HAS_PKEYS
|
bool
|
|
config PERCPU_STATS
|
bool "Collect percpu memory statistics"
|
help
|
This feature collects and exposes statistics via debugfs. The
|
information includes global and per chunk statistics, which can
|
be used to help understand percpu memory usage.
|
|
config ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT
|
def_bool n
|
|
config SPECULATIVE_PAGE_FAULT
|
bool "Speculative page faults"
|
default y
|
depends on ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT
|
depends on MMU && SMP && !NUMA
|
help
|
Try to handle user space page faults without holding the mmap_sem.
|
|
This should allow better concurrency for massively threaded process
|
since the page fault handler will not wait for other threads memory
|
layout change to be done, assuming that this change is done in another
|
part of the process's memory space. This type of page fault is named
|
speculative page fault.
|
|
If the speculative page fault fails because of a concurrency is
|
detected or because underlying PMD or PTE tables are not yet
|
allocating, it is failing its processing and a classic page fault
|
is then tried.
|
|
config GUP_BENCHMARK
|
bool "Enable infrastructure for get_user_pages() and related calls benchmarking"
|
help
|
Provides /sys/kernel/debug/gup_benchmark that helps with testing
|
performance of get_user_pages() and related calls.
|
|
See tools/testing/selftests/vm/gup_benchmark.c
|
|
config GUP_GET_PTE_LOW_HIGH
|
bool
|
|
config READ_ONLY_THP_FOR_FS
|
bool "Read-only THP for filesystems (EXPERIMENTAL)"
|
depends on TRANSPARENT_HUGEPAGE && SHMEM
|
|
help
|
Allow khugepaged to put read-only file-backed pages in THP.
|
|
This is marked experimental because it is a new feature. Write
|
support of file THPs will be developed in the next few release
|
cycles.
|
|
config ARCH_HAS_PTE_SPECIAL
|
bool
|
|
#
|
# Some architectures require a special hugepage directory format that is
|
# required to support multiple hugepage sizes. For example a4fe3ce76
|
# "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
|
# introduced it on powerpc. This allows for a more flexible hugepage
|
# pagetable layouts.
|
#
|
config ARCH_HAS_HUGEPD
|
bool
|
|
config MAPPING_DIRTY_HELPERS
|
bool
|
|
source "mm/damon/Kconfig"
|
|
config KMAP_LOCAL
|
bool
|
|
endmenu
|
